• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1525-1533
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• 2003

In the precision hot plate for wafer processing, uniform temperature of the upper plate is one of key factors affecting the quality of wafers. The state-of-the-art precision hot plates require temperature Variations less than $\pm$0.4$^{\circ}C$ during heating to 15$0^{\circ}C$, Which is difficult to be obtained only by the improvement of manufacturing techniques alone. In this study, computer aided heat transfer analysis was carried out to obtain the temperature distribution of the currently used reference hot plate for 200mm wafer. The analysis on the reference model assuming constant heat generation rate and uniform heating area showed total variation of 0.926$^{\circ}C$ at 15$0^{\circ}C$. One of the new design approaches based on the change of heating location together with different heat generation rate resulted in total variation of 0.297$^{\circ}C$ which is a 68% improvement compared to that of the reference model.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.591-597
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• 2014

A poled lead zirconate titanate (PZT) rectangular parallelepiped specimen was subjected to through-thickness electric fields at five loading rates and four temperatures. The rates of the electric field were 0.01, 0.10, 0.25, 0.50, and $1.00MVm^{-1}s^{-1}$; the temperatures were 20, 50, 80, and $110^{\circ}C$. From the measured polarization hysteresis responses, the so-called reference remnant polarization and strains were calculated. Using the calculated reference remnant polarization hysteresis loops, the effects of loading rates and temperature were discussed; using the calculated reference remnant strains, strain butterfly loops were calculated and compared with observations.

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.69-71
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• 1993

Fluoride compound potentiometric cell oxygen sensors were fabricated for the measurement of oxygen pressure in the low temperature range (300。K-500。K). The disk type sensors consist of a reference Air(0$_2$):Ag, a solid electrolyte SrF$_2$, and a sensing metel Ag electrode. And the buried reference electrode type sensor have a NiO/Ni reference electrode. The open circuit emf of the cell showed high sensivity to oxygen gas (60mv) at the measuring temperature 20$0^{\circ}C$. Also, The buried reference electrode type sensor showed 30mv from 1% to 10% oxygen pressure range.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.4
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• pp.87-94
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• 2004

Recently, technical trend in machine tools is focused on enhancing of speed, accuracy and reliability. The high speed usually results in thermal displacement and structural deformation. To minimize the thermal effect, precision machine tools adopt a high precision cooling system. This study proposes a temperature control for an oil cooler system using Pill control with fuzzy logic. In the cooler system, refrigerant flow rate is controlled by rotational speed of a compressor, and outlet oil temperature is selected as the control variable. The fuzzy control rules iteratively correct PID parameters to minimize the error and difference between the outlet temperature and the reference temperature. Here, ambient temperature is used as the reference one. To show the effectiveness of the proposed method, a series of experiments are conducted for an oil cooler system of machine tools, and the results are compared with the ones of a conventional Pill control. The experimental results show that the proposed method has advantages of faster response and smaller overshoot.

• Journal of IKEEE
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• v.20 no.2
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• pp.192-195
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• 2016

In this paper, we present a nanopower CMOS bandgap voltage reference working in sub-threshold region without resisters and bipolar junction transistors (BJT). Complimentary to absolute temperature (CTAT) voltage generator was realized by using two n-MOSFET pair with body bias circuit to make a sufficient amount of CTAT voltage. Proportional to absolute temperature (PTAT) voltage was generated from differential amplifier by using different aspect ratio of input MOSFET pair. The proposed circuits eliminate the use of resisters and BJTs for the operation in a sub-1V low supply voltage and for small die area. The circuits are implemented in 0.18um standard CMOS process. The simulation results show that the proposed sub-BGR generates a reference voltage of 290mV, obtaining temperature coefficient of 92 ppm/$^{\circ}C$ in -20 to $120^{\circ}C$ temperature range. The circuits consume 15.7nW at 0.63V supply.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.527-530
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• 2016

This paper presents curvature-compensated reference circuits operating under low-voltage condition and achieving low-power consumption with $0.35-{\mu}m$ standard CMOS process. The proposed circuit can operate under less than 1-V supply voltage by using MOS transistors operating in weak-inversion region. The simulation results shows a low temperature coefficient by using the proposed curvature compensation technique. It generates a graph-shape temperature characteristic that looks like a sine curve, not a bell-shape characteristic presented in other published BGRs without curvature compensation. The proposed circuits operate with 0.9-V supply voltage. First, the voltage reference circuit consumes 176nW power and the temperature coefficient is $26.4ppm/^{\circ}C$. The current reference circuit is designed to operate with 194.3nW power consumption and $13.3ppm/^{\circ}C$ temperature coefficient.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.9 no.4
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• pp.141-146
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• 2010

In this paper, bandgap reference PTAT(Proportional to Absolute Temperature) circuit and flexible gain control of LNA(Low Noise Amplifier) which is usable in Zigbee system of 2.4GHz band are designed by TSMC $0.18{\mu}m$ CMOS library. PTAT bandgap reference circuit is proposed to minimize the instability of CMOS circuit which may be unstable in temperature changes. This circuit is designed such that output voltage remains within 1.3V even when the temperature varies from $-40^{\circ}C$ to $-50^{\circ}C$ when applied to the gate bias voltage of LNA. In addition, the LNA is designed to be operated on 2.4GHz which is applicable to Zigbee system and able to select gains by changing output impedance using 4 NMOS operated switches. The simulation result shows that achieved gain is 14.3~17.6dB and NF (Noise Figure) 1.008~1.032dB.

• Transactions on Electrical and Electronic Materials
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• v.5 no.2
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• pp.71-75
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• 2004

This paper proposes a new bandgap reference (BGR) circuit which takes advantage of a cascode current mirror biasing to reduce the V$\_$ref/ variation, and sizing technique, which utilizes two related ratio numbers k and N, to reduce the PNP BJT area. The proposed BGR is designed and fabricated on a test chip with a goal to provide a reference voltage to the 10 bit A/D(4-4-4 pipeline architecture) converter of the CMOS Active Pixel Sensor (APS) imager to be used in X-ray imaging. The basic temperature variation effect on V$\_$ref/ of the BGR has a maximum delta of 6 mV over the temperature range of 25$^{\circ}C$ to 70$^{\circ}C$. To verify that the proposed BGR has radiation hardness for the X-ray imaging application, total ionization dose (TID) effect under Co-60 exposure conditions has been evaluated. The measured V$\_$ref/ variation under the radiation condition has a maximum delta of 33 mV over the range of 0 krad to 100 krad. For the given voltage, temperature, and radiation, the BGR has been satisfied well within the requirement of the target 10 bit A/D converter.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.3
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• pp.67-71
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• 2024

A smart window based on a retarder can transmit or block polarized lights by overlapping two smart windows. In the study, tests were conducted to evaluate the performance of blocking solar heat using smart windows with a size of 300×300 mm². Solar heat gain coefficient (SHGC) values were derived through simulation using transmission and reflectance data of the smart windows. As a result of the simulation, it showed that SGHC is effective in blocking solar heat by obtaining values of 0.722 and 0.615 in transmission and blocking mode of smart windows, respectively. The test boxes were fabricated in order to verify the effect of suppressing temperature rise when applying smart windows, the inside temperature in test boxes, which are installed bare glass (reference) and two smart windows with transmission and blocking mode, were measured at 10 minutes-interval for 7 days. As of 1 p.m., the inside temperature of the test boxes with the smart windows applied showed lower temperature compared to the reference. In particular, on the day when the temperature of reference box was the highest at 66.1℃, the temperature of the test box with the smart window applied showed 61.0℃, which was lowered by 5.1℃.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.376-380
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• 2006

Temperature distribution measured to estimate the condition of an electrical apparatus is an absolute reference for the apparatus conditions and the difference between the reference temperature and the current temperature. Because of passive thermography, without the external thermal stimulation, the difference in surface temperature between the region of interest and back ground shows that the results can apply only to the estimation or the monitoring for the condition of loose terminal and the overload pertaining to the rise in temperature. However, a thermal diffusion in the active thermography is differently generated by the structure and condition of the surface and subsurface. This paper presents a nondestructive test using this behavior and deals with the results by heat injection and cooling to the apparatus. The buried discontinuity of subsurface could be detected by these techniques.